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Discussion Starter #1
A while back I had an unfortunate incident when I was sighting in my new vortex razor hd scope on my 17 .The bolt slammed so hard into the rear it cracked my bolt carrier. I was running it exclusively suppressed with the stock gas jet for years without issue until this happened. Needless to say I was not happy. I sent the rifle off to FN (despite it being very obvious I had voided the warranty) they got me a new BC, new receiver screws (mine were canted baaaad), and new end plate. It cost me $600, but they are the only ones to get BC's from.

Long story short, tune your scar if you're shooting suppressed, and mark your receiver screws to make sure the bolt isnt slamming too hard back. LEARN FROM MY DUMBASS MISTAKE!
 

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OK, I'll bite! I have a suppressor and want to use it but if I'm being honest, have no idea to what you're referring above re: stock gas jet. Am I to change something to run suppressed? Seems odd. Also, why 'mark receiver screws'?
I just got my Scar and frankly when I read stuff like this, it makes me want to go back to an AR10. Shouldn't a $3K gun already be suited for a suppressor and not require constant vigilance over every little detail? Or am I over-estimating your advice?
 

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I have to admit that looks bad but how do you know what caused it other than taking a guess. There are so many SCARS out there that use suppressors with stock jets and not having this problem. I would question if this is just a one of a kind failure. I have shot a lot of rounds through my suppressor with a stock jet and no problem.
TBrown, may I ask what ammo you use with the suppressor.
 

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Discussion Starter #4
stock gas jet size is 1.5 mm on a 16" 17. Part of the issue on these piston guns like the scar is that the back pressure caused by using a suppressor causes the bolt to slam back into the receiver plate harder than it should causing your receiver screws to cant or back out as well as running the risk of shearing your bolt carrier like I did. By swapping out the gas jet for a different size you can eliminate some of the harsh recoil when shooting suppressed and lessen the damage to your bolt carrier and felt recoil. I assume the 1.5 jet was picked by FN in order to make damn sure that the rifle would cycle with any type of ammo.

Hope that answered your questions. Also cleaning the piston and removing some of the buildup is a good idea every few cleanings, something I neglected and ultimately paid for....literally
 

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Discussion Starter #5
I have to admit that looks bad but how do you know what caused it other than taking a guess. There are so many SCARS out there that use suppressors with stock jets and not having this problem. I would question if this is just a one of a kind failure. I have shot a lot of rounds through my suppressor with a stock jet and no problem.
TBrown, may I ask what ammo you use with the suppressor.
I run a 762 SDN6 can and a variety of ammo, I think always having it suppressed and neglecting to clean the piston had something to do with it. I also used to have the KDG scar stock on the rifle, after shooting with that on for a while I really noticed the screws canting. I promptly got rid of it and went OEM stock. I know plenty of guys run the stock jet and have no issues but I thought I would share my experience to potentially help someone avoid the hassle of a sheared BC
 

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What does it take to change out the jet? Where can one be purchased and if so, are there multiple options? Sorry for all the questions but I'm clearly uneducated and do want to run this suppressed more often than not. I have a Vltor stock fwiw. I'll get online and see if i can find more intel on my own when I ever get some time!
 

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Last weekend I took my SCAR 17 to the range for a final shakedown with various magazines & gas jets. First, specifics of the rifle:

SCAR 17
20" FN barrel w/Surefire WARCOMP Flash Hider
Handl Defense Aluminum Lower w/Geissele Super Scar Trigger
Mototecw
h Soft Rubber Buffer
Northtech Folding Charging Handle
KDG SAS Folding Stock
ELCAN SpecterDR 1.5/6.0 Sight

Magazines:
Magpul LR/SR M118 25 rd. Polymer
DPMS AR-10 20 rd. Steel
Hexmag AR-10 20 rd. Polymer
C Products Defense AR-10 Stainless Steel Coated

Gas Jets:
PMM 1.20, 1.25, 1.30, 1.35, 1.40, Factory FN Jet w/20" Barrel (Size Unknown), Handl Defense 1.64, 1.70 & 2.30.

On the initial trip to the range I only had the factory stock rifle with the 20" barrel and the Magpul Mags. Empty or fully loaded mags were extremely tight fit and would not latch, ever. You could see on the exterior poly "band" of the mags where they were interfering with the magwell of the lower in several places. So much for the Magpuls, they're garbage for my situation.

Next
weekend out, the same setup as the first except a DPMS AR-10 mag and a 1.20 gas jet installed. Consistent failures to feed and no bolt hold open with the 1.20, 1.25, 1.30, 1.35 jets. With the 1.40 and 1.50 jets there were no failures to feed except for the LAST round and still no bolt hold open. So much for the DPMS mags.

Last weekend, same setup as above except with Hexmag & C Products Defense magazines. Consistent failures to feed & no bolt hold open with both mags using the 1.20, 1.25, 1.30. With the 1.35 & 1.40 jets the Hexmag would feed all rounds except the LAST round, so not bolt hold open either. With both the 1.35 & 1.40 jets the C Products Defense mags fed ALL the rounds and held the bolt open after the last shot. Called it a day at that point.

Saturday it'll be a head-to-head test of 100 rds. each with the 1.35 & 1.40 jets & the C Products Defense mags. Something tells me that the 1.40 jet will be the sweet spot for my rifle, but I might be surprised. I still haven't been able to find out what size jet the 20" barrel ships with, so it's possible that I've had a substantial reduction in the size of the gas jet from the factory one, or not. Does anybody know what size jet comes with the 20" barrel?

As soon as my Surefire RC2 arrives I'll start the process all over again to find the "perfect" suppressor setting and after this weekend's trip to the range I'll check the bolt, recoil plate and screws to see if I can see any issues with them.

Kinda funny though that a lot of folks that complain about the recoil of the SCAR probably haven't spent much "quality" time with a Garand, M14, HK91 or Galil ARM. The only adjustment & tuning provided on them is done with the shoulder!!!








https://kineticdg.com/product/scarsasstockbrown/
 

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I also used to have the KDG scar stock on the rifle, after shooting with that on for a while I really noticed the screws canting. I promptly got rid of it and went OEM stock.
If I had to take an uneducated guess I would say above is what started the whole issue. The old 6061-T6 aluminum adapter on the KDG vs the OEM polymer stock. Slam Slam! Bam Bam!

Also, were you changing the gas regulator to the "suppressed" setting?

I'm no engineer but I don't believe the receiver screws did that to your bolt carrier. It looks like a constant suppressed beating of rearward force into the KDG aluminum stock hinge caused it.

This probably produced a small crack. Even though you went back to the OEM stock it got worse over time running it with the can.
 

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Discussion Starter #11
If I had to take an uneducated guess I would say above is what started the whole issue. The old 6061-T6 aluminum adapter on the KDG vs the OEM polymer stock. Slam Slam! Bam Bam!

Also, were you changing the gas regulator to the "suppressed" setting?

I'm no engineer but I don't believe the receiver screws did that to your bolt carrier. It looks like a constant suppressed beating of rearward force into the KDG aluminum stock hinge caused it.

This probably produced a small crack. Even though you went back to the OEM stock it got worse over time running it with the can.
I know the receiver screws didn't cause my bolt to crack , the slamming just made them cant. The KDG stock definitely accelerated the bolt wear, I also really started noticing the harsher recoil when I put it on.

I always kept the gun in a suppressed setting, I never shoot it unsuppressed.
 

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Good info to share with us TBROWN 1911. I was using the VLTOR receiver extension on mine for a while - with a buffer from HDD. I had noticed my screws loosened up before I got the buffer - but the buffer seemed to stop any ill effects. Either way, I went back to the OEM butt stock, just because all the warnings on this forum made me feel uneasy. Your experience takes the cake, and the pics - worth a thousand words. I don't shoot suppressed, perhaps in the future who knows. But I'll just stick with the OEM stock after seeing your post I believe. Glad you've got your 17 up and running again, great looking rifle you got there ! (It's only March - but I'd say the lessons learned from your pics give you the post of the year award so far)
 

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You have to be a FNH-trained armourer, or lucky enough to find the perfect mix of gas jet, suppressor back pressure, and ammunition to avoid the damage you are causing the weapon. 5,000 total rounds of factory ammo (last 1,000 suppressed) resulted in the same damage to my 17. Again, if your source of income is from FNH USA as one of their armourers then you *might* be able to avoid a BC failure. Otherwise, you're only delaying the inevitable bolt carrier failure and binding in the receiver. I was lucky that they only had to replace the BC, cam pin, rail, and screws for the rail at a cost of near $600 and 3 weeks. Complaints about how much it costs and that it has a "suppressed" regulator setting don't override what FNH told me when I read the manual for the first time after I bought the weapon. I again enjoy making my fellow range users move away to avoid the noise and pressure of this beast. You've been warned.
 

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You have to be a FNH-trained armourer, or lucky enough to find the perfect mix of gas jet, suppressor back pressure, and ammunition to avoid the damage you are causing the weapon. 5,000 total rounds of factory ammo (last 1,000 suppressed) resulted in the same damage to my 17. Again, if your source of income is from FNH USA as one of their armourers then you *might* be able to avoid a BC failure. Otherwise, you're only delaying the inevitable bolt carrier failure and binding in the receiver. I was lucky that they only had to replace the BC, cam pin, rail, and screws for the rail at a cost of near $600 and 3 weeks. Complaints about how much it costs and that it has a "suppressed" regulator setting don't override what FNH told me when I read the manual for the first time after I bought the weapon. I again enjoy making my fellow range users move away to avoid the noise and pressure of this beast. You've been warned.

Viking187, out of curiosity, did you ever run an aluminum butt stock on your rifle ?
 

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Thank You TBROWN 1911 for posting this. I have wanted a Scar 17S for quite awhile, and I now have one. I also have recently purchased my second suppressor, a Silencer Co. Hybrid 46 pending approval, but I may need to go with either the Surefire Socom RCII or the Dead Air Sandman S. I had stupidly thought the Hybrid would be a one suppressor to rule them all, should have known better. I truly wish FN would just release a dedicated suppressor for the Scar 17S, so we all would could live happily ever after in Suppressed Scarland. With all the issues I have seen with suppressors of late, being the newbie that I am , I am not sure I even want to suppress my Scar now that I have one.
 

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With ya and frankly quite a bit disappointed that the bulletproof scar is dodgy using suppressors? How did I miss this when deciding to sell an AR10 that I loved and getting the Scar? To confidently run suppressed, must I go back to friggin’ square one?! I know what site I’m on and this isn’t my first Scar so flame away if you must but the confidence I had in having ‘the best battle rifle’ (and paying for it I might add), is all but lost. Thinking about ditching and going back to trusty PWS MK216.
can anyone talk me out of it? Am I making too much of this?
 

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If memory serves, every issue I've seen regarding suppressed use with the 17s has included installation of a non OEM stock at some point.

I could be wrong.

Everyone is like, "I reconfigured the flux capacitor and it blew up!" "Bad 17s, bad..."
 

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I bought mine slightly used with a Vltor stock....but it also came with the OEM stock (which having had in the past, I didn't mind) so I'll just go with that and watch things as best I can. I'm far from an Armorer but suppose I can find a video someplace describing the issue and what to look for? Between here and on AR15, I'm sure I can get 'schooled'.
 
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